Sporadic Form Of Amyotrophic Lateral Sclerosis Research Articles

Juvenile amyotrophic lateral sclerosis caused by a mutation in the SPTLC2 gene: case presentation

Juvenile amyotrophic lateral sclerosis (ALS) is a rare group of motor neuron diseases, with the age of onset up to 25 years. Juvenile ALS more commonly has genetic origin vs. sporadic forms of ALS that develop in adulthood. Genetic analysis of these cases with early onset makes it possible to identify the genes responsible for the disease. Here we present a case of a rare variant of juvenile ALS caused due to the SPTLC2 gene mutation.
 Cases with early disease onset are characterized by slow progression and variable phenotype, which often makes accurate diagnosis challenging. Therefore patients with combined upper and lower motor neuron disorders aged under 25 years should undergo comprehensive examination, in particular to identify gene mutations.

Oligodendroglia Confer Neuroprotection to NSC-34 Motor Neuronal Cells Against the Toxic Insults of Cerebrospinal Fluid from Sporadic Amyotrophic Lateral Sclerosis Patients.

Amyotrophic lateral sclerosis (ALS) is a complex neurodegenerative disorder with multifactorial pathomechanisms affecting not only motor neurons but also glia. Both astrocytes and microglia get activated and contribute significantly to neurodegeneration. The role of oligodendroglia in such a situation remains obscure, especially in the sporadic form of ALS (SALS), which contributes to 90% of cases. Here, we have investigated the role of oligodendroglia in SALS pathophysiology using a human oligodendroglial cell line, MO3.13, by exposing the cells to cerebrospinal fluid from SALS patients (ALS-CSF; 10% v/v for 48 h). ALS-CSF significantly reduced the viability of MO3.13 cells and down-regulated the expression of oligodendroglia-specific proteins, namely, CNPase and Olig2. Furthermore, to investigate the effect of the observed oligodendroglial changes on motor neurons, NSC-34 motor neuronal cells were co-cultured/supplemented with conditioned/spent medium of MO3.13 cells upon exposure to ALS-CSF. Live cell imaging experiments revealed protection to NSC-34 cells against ALS-CSF toxicity upon co-culture with MO3.13 cells. This was evidenced by the absence of neuronal cytoplasmic vacuolation and beading of neurites, which instead resulted in better neuronal differentiation. Enhanced lactate levels and increased expression of its transporter, MCT-1, with sustained expression of trophic factors, namely, GDNF and BDNF, by MO3.13 cells hint towards metabolic and trophic support provided by the surviving oligodendroglia. Similar metabolic changes were seen in the lumbar spinal cord oligodendroglia of rat neonates intrathecally injected with ALS-CSF. The findings indicate that oligodendroglia are indeed rescuer to the degenerating motor neurons when the astrocytes and microglia turn topsy-turvy.

Antisense Oligonucleotides for the Study and Treatment of ALS.

Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disease characterized by motor neuron loss. ALS is now associated with mutations in numerous genes, many of which cause disease in part through toxic gain-of-function mechanisms. Antisense oligonucleotides (ASOs) are small sequences of DNA that can reduce expression of a target gene at the post-transcriptional level, making them attractive for neutralizing mutant or toxic gene products. Advancements in the medicinal chemistries of ASOs have improved their pharmacodynamic profile to allow safe and effective delivery to the central nervous system. ASO therapies for ALS have rapidly developed over the last two decades, and ASOs that target SOD1, C9orf72, FUS, and ATXN2 are now in clinicaltrials for familial or sporadic forms of ALS. This review discusses the current state of ASO therapies for ALS, outlining their successes from preclinical development to early clinical trials.

TDP-43 regulates cholesterol biosynthesis by inhibiting sterol regulatory element-binding protein 2

Dyslipidemia is considered an essential component of the pathological process of amyotrophic lateral sclerosis (ALS), a fatal motor neuron disease. Although TAR DNA Binding Protein 43 kDa (TDP-43) links both familial and sporadic forms of ALS and cytoplasmic aggregates are a hallmark of most cases of ALS, the molecular mechanism and the in vivo relation of ALS dyslipidemia with TDP-43 have been unclear. To analyze the dyslipidemia-related gene expression by TDP-43, we performed expression microarray and RNA deep sequencing (RNA-Seq) using cell lines expressing high levels of TDP-43 and identified 434 significantly altered genes including sterol regulatory element-binding protein 2 (SREBP2), a master regulator of cholesterol homeostasis and its downstream genes. Elevated TDP-43 impaired SREBP2 transcriptional activity, leading to inhibition of cholesterol biosynthesis. The amount of cholesterol was significantly decreased in the spinal cords of TDP-43-overexpressed ALS model mice and in the cerebrospinal fluids of ALS patients. These results suggested that TDP-43 could play an essential role in cholesterol biosynthesis in relation to ALS dyslipidemia.

Diagnostic Circulating miRNAs in Sporadic Amyotrophic Lateral Sclerosis.

Amyotrophic Lateral Sclerosis (ALS) is a fatal neurodegenerative disease characterized by the neurodegeneration of motoneurons. About 10% of ALS is hereditary and involves mutation in 25 different genes, while 90% of the cases are sporadic forms of ALS (sALS). The diagnosis of ALS includes the detection of early symptoms and, as disease progresses, muscle twitching and then atrophy spreads from hands to other parts of the body. The disease causes high disability and has a high mortality rate; moreover, the therapeutic approaches for the pathology are not effective. miRNAs are small non-coding RNAs, whose activity has a major impact on the expression levels of coding mRNA. The literature identifies several miRNAs with diagnostic abilities on sALS, but a unique diagnostic profile is not defined. As miRNAs could be secreted, the identification of specific blood miRNAs with diagnostic ability for sALS could be helpful in the identification of the patients. In the view of personalized medicine, we performed a meta-analysis of the literature in order to select specific circulating miRNAs with diagnostic properties and, by bioinformatics approaches, we identified a panel of 10 miRNAs (miR-193b, miR-3911, miR-139-5p, miR-193b-1, miR-338-5p, miR-3911-1, miR-455-3p, miR-4687-5p, miR-4745-5p, and miR-4763-3p) able to classify sALS patients by blood analysis. Among them, the analysis of expression levels of the couple of blood miR-193b/miR-4745-5p could be translated in clinical practice for the diagnosis of sALS.

Novel Genetic Signatures Associated With Sporadic Amyotrophic Lateral Sclerosis.

Amyotrophic Lateral Sclerosis (ALS) is a complex polygenetic neurodegenerative disorder. Establishing a diagnosis for ALS is a challenging and lengthy process. By the time a diagnosis is made, the lifespan prognosis is only about two to 5 years. Genetic testing can be critical in assessing a patient’s risk for ALS, provided they have one of the known familial genes. However, the vast majority of ALS cases are sporadic and have no known associated genetic signatures. Our analysis of the whole genome sequencing data from ALS patients and healthy controls from the Answer ALS Consortium has uncovered twenty-three novel mutations in twenty-two protein-coding genes associated with sporadic ALS cases. The results show the majority of patients with the sporadic form of ALS have at least one or more mutation(s) in the 22 genes we have identified with probabilities of developing ALS ranging from 25–99%, depending on the number of mutations a patient has among the identified genes. Moreover, we have identified a subset of the ALS cohort that has >17 mutations in the 22 identified. In this case, a patient with this mutation profile has a 99% chance of developing ALS and could be classified as being at high risk for the disease. These genetic biomarkers can be used as an early ALS disease diagnostic tool with a rapid and non-invasive technique.

Reduced mitochondrial D-loop methylation levels in sporadic amyotrophic lateral sclerosis

BackgroundMitochondrial dysregulation and aberrant epigenetic mechanisms have been frequently reported in neurodegenerative diseases, including amyotrophic lateral sclerosis (ALS), and several researchers suggested that epigenetic dysregulation in mitochondrial DNA (mtDNA) could contribute to the neurodegenerative process. We recently screened families with mutations in the major ALS causative genes, namely C9orf72, SOD1, FUS, and TARDBP, observing reduced methylation levels of the mtDNA regulatory region (D-loop) only in peripheral lymphocytes of SOD1 carriers. However, until now no studies investigated the potential role of mtDNA methylation impairment in the sporadic form of ALS, which accounts for the majority of disease cases. The aim of the current study was to investigate the D-loop methylation levels and the mtDNA copy number in sporadic ALS patients and compare them to those observed in healthy controls and in familial ALS patients. Pyrosequencing analysis of D-loop methylation levels and quantitative analysis of mtDNA copy number were performed in peripheral white blood cells from 36 sporadic ALS patients, 51 age- and sex-matched controls, and 27 familial ALS patients with germinal mutations in SOD1 or C9orf72 that represent the major familial ALS forms.ResultsIn the total sample, D-loop methylation levels were significantly lower in ALS patients compared to controls, and a significant inverse correlation between D-loop methylation levels and the mtDNA copy number was observed. Stratification of ALS patients into different subtypes revealed that both SOD1-mutant and sporadic ALS patients showed lower D-loop methylation levels compared to controls, while C9orf72-ALS patients showed similar D-loop methylation levels than controls. In healthy controls, but not in ALS patients, D-loop methylation levels decreased with increasing age at sampling and were higher in males compared to females.ConclusionsPresent data reveal altered D-loop methylation levels in sporadic ALS and confirm previous evidence of an inverse correlation between D-loop methylation levels and the mtDNA copy number, as well as differences among the major familial ALS subtypes. Overall, present results suggest that D-loop methylation and mitochondrial replication are strictly related to each other and could represent compensatory mechanisms to counteract mitochondrial impairment in sporadic and SOD1-related ALS forms.

Modelling a Novel Superoxide Dismutase 1 Mutation in Motor Neurons: An Insight into Molecular Pathomechanism of Amyotrophic Lateral Sclerosis

Amyotrophic lateral sclerosis (ALS) is a fatal, adult onset neurological disorder characterized by progressive degeneration of upper and lower motor neurons. ALS is a multifactorial disease with a complex etiology and misfolded protein aggregates are considered as the major neuropathological hallmark. Several genetic mutations are associated with familial and sporadic forms of ALS. We have recently reported the first mutation in Superoxide Dismutase 1 (SOD1) in a family with ALS from India. The purpose of this study is to explore the functional consequences of L84F SOD1 mutation using in‐vitro cell model. We observed that this novel triallelic mutation (L84F) caused metal chelation and destabilized the native SOD1 dimer. Cells expressing mutant SOD1 showed increased protein carbonylation and were more sensitive to oxidative stress. Further, L84F SOD1 mutant readily formed detergent‐resistant aggregates in motor neuronal cell line. Modulating protein homeostasis pathways led to enhanced aggregation of mutant SOD1. Interestingly, the cells expressing mutant SOD1 exhibited significant decrease in neuronal differentiation compared to wild type. Our data shows that altered differentiation in mutant SOD1 cells is probably due to hampered autophagy and aberrant deposition of misfolded protein. We also observed that treatment with flavonoids including curcumin, luteolin abolished mutant SOD1 aggregates by inducing autophagy.ALS pathology also involves disassembly of neuromuscular junction (NMJ) which leads to muscle atrophy. However, the series of events that leads to skeletal muscle denervation is poorly understood. To examine the effect of mutant SOD1 on NMJ, we have established an in‐vitro NMJ model by co‐culturing skeletal muscle and motor neuronal cells. We are currently using this model to delineate the neuron‐ and muscle‐ specific cues that affects the structural and functional integrity of NMJ. To conclude, L84F SOD1 mutant exhibits characteristics of ALS such as aggregation of misfolded protein and deregulated proteasome machinery. Further targeting protein homeostasis pathways may aid in developing novel therapeutics for ALS.Support or Funding InformationAuthors acknowledge Indian Council of Medical Research (ICMR) (Project Code: 1.3.2.183.025) and Research Development Program (RDP) at Sir Ganga Ram Hospital for funding the research project. SV acknowledges Council of Scientific and Industrial Research (CSIR) and AV, SK acknowledges Indian Council of Medical Research (ICMR) for fellowships.

Dysregulation of AMPA receptor subunit expression in sporadic ALS post-mortem brain.

Amyotrophic lateral sclerosis (ALS) is characterised by progressive motor neuron degeneration. Although there are over 40 genes associated with causal monogenetic mutations, the majority of ALS patients are not genetically determined. Causal ALS mutations are being increasingly mechanistically studied, though how these mechanisms converge and diverge between the multiple known familial causes of ALS (fALS) and sporadic forms of ALS (sALS) and furthermore between different neuron types, is poorly understood. One common pathway that is implicated in selective motor neuron death is enhanced α‐amino‐3‐hydroxyl‐5‐methyl‐4‐isoxazole‐propionate (AMPAR)‐mediated excitoxicity. Specifically, human in vitro and pathological evidence has linked the C9orf72 repeat expansion mutation to a relative increase in the Ca2+‐permeable AMPAR population due to AMPAR subunit dysregulation. Here, we provide the first comparative quantitative assessment of the expression profile of AMPAR subunit transcripts, using BaseScope, in post‐mortem lower motor neurons (spinal cord, anterior horn), upper motor neurons (motor cortex) and neurons of the pre‐frontal cortex in sALS and fALS due to mutations in SOD1 and C9orf72. Our data indicated that AMPAR dysregulation is prominent in lower motor neurons in all ALS cases. However, sALS and mutant C9orf72 cases exhibited GluA1 upregulation whereas mutant SOD1 cases displayed GluA2 down regulation. We also showed that sALS cases exhibited widespread AMPAR dysregulation in the motor and pre‐frontal cortex, though the exact identity of the AMPAR subunit being dysregulated was dependent on brain region. In contrast, AMPAR dysregulation in mutant SOD1 and C9orf72 cases was restricted to lower motor neurons only. Our data highlight the complex dysregulation of AMPAR subunit expression that reflects both converging and diverging mechanisms at play between different brain regions and between ALS cohorts. © 2019 Authors. Journal of Pathology published by John Wiley & Sons Ltd on behalf of Pathological Society of Great Britain and Ireland.

Mitochondrial Transport and Turnover in the Pathogenesis of Amyotrophic Lateral Sclerosis.

Neurons are high-energy consuming cells, heavily dependent on mitochondria for ATP generation and calcium buffering. These mitochondrial functions are particularly critical at specific cellular sites, where ionic currents impose a large energetic burden, such as at synapses. The highly polarized nature of neurons, with extremely large axoplasm relative to the cell body, requires mitochondria to be efficiently transported along microtubules to reach distant sites. Furthermore, neurons are post-mitotic cells that need to maintain pools of healthy mitochondria throughout their lifespan. Hence, mitochondrial transport and turnover are essential processes for neuronal survival and function. In neurodegenerative diseases, the maintenance of a healthy mitochondrial network is often compromised. Numerous lines of evidence indicate that mitochondrial impairment contributes to neuronal demise in a variety of neurodegenerative diseases, including amyotrophic lateral sclerosis (ALS), where degeneration of motor neurons causes a fatal muscle paralysis. Dysfunctional mitochondria accumulate in motor neurons affected by genetic or sporadic forms of ALS, strongly suggesting that the inability to maintain a healthy pool of mitochondria plays a pathophysiological role in the disease. This article critically reviews current hypotheses on mitochondrial involvement in the pathogenesis of ALS, focusing on the alterations of mitochondrial axonal transport and turnover in motor neurons.

Histological changes in the rat brain and spinal cord following prolonged intracerebroventricular infusion of cerebrospinal fluid from amyotrophic lateral sclerosis patients are similar to those caused by the disease

IntroductionCerebrospinal fluid (CSF) from amyotrophic lateral sclerosis (ALS) patients induces cytotoxic effects in in vitro cultured motor neurons. Materials and methodsWe selected CSF with previously reported cytotoxic effects from 32 ALS patients. Twenty-eight adult male rats were intracerebroventricularly implanted with osmotic mini-pumps and divided into 3 groups: 9 rats injected with CSF from non-ALS patients, 15 rats injected with cytotoxic ALS-CSF, and 4 rats injected with a physiological saline solution. CSF was intracerebroventricularly and continuously infused for periods of 20 or 43days after implantation. We conducted clinical assessments and electromyographic examinations, and histological analyses were conducted in rats euthanised 20, 45, and 82days after surgery. ResultsImmunohistochemical studies revealed tissue damage with similar characteristics to those found in the sporadic forms of ALS, such as overexpression of cystatin C, transferrin, and TDP-43 protein in the cytoplasm. The earliest changes observed seemed to play a protective role due to the overexpression of peripherin, AKTpan, AKTphospho, and metallothioneins; this expression had diminished by the time we analysed rats euthanised on day 82, when an increase in apoptosis was observed. The first cellular changes identified were activated microglia followed by astrogliosis and overexpression of GFAP and S100B proteins. ConclusionOur data suggest that ALS could spread through CSF and that intracerebroventricular administration of cytotoxic ALS-CSF provokes changes similar to those found in sporadic forms of the disease.

Prion Properties of SOD1 in Amyotrophic Lateral Sclerosis and Potential Therapy.

Amyotrophic lateral sclerosis (ALS) is a devastating and rapidly progressive neurodegenerative disease caused by the deterioration of motor neurons. The first symptoms of ALS always begin at a focal but variable site and consistently spread to neighboring regions, suggesting that neurodegeneration in ALS is an orderly and propagating process. Like other neurodegenerative diseases, misfolding of a specific protein is central to ALS. SOD1, the major constituent of the protein deposits in some familial and sporadic forms of ALS, propagates its misfolded conformation like prions, providing a plausible molecular basis for the focality and spreading of muscle weakness in ALS. Because protein misfolding is a common cause of diverse neurodegenerative diseases, strategies aimed at boosting a cell's ability to cope with misfolded proteins could lead to therapeutics to combat these devastating age-related proteinopathies.

La infusión intracerebroventricular prolongada de líquido cefalorraquídeo procedente de pacientes con esclerosis lateral amiotrófica provoca cambios histológicos en el cerebro y la médula espinal de la rata similares a los hallados en la enfermedad

IntroductionCerebrospinal fluid (CSF) from amyotrophic lateral sclerosis (ALS) patients induces cytotoxic effects in in vitro cultured motor neurons. Material and methodsWe selected CSF with previously reported cytotoxic effects from 32 ALS patients. Twenty-eight adult male rats were intracerebroventricularly implanted with osmotic mini-pumps and divided into 3 groups: 9 rats injected with CSF from non-ALS patients, 15 rats injected with cytotoxic ALS-CSF, and 4 rats injected with a physiological saline solution. CSF was intracerebroventricularly and continuously infused for periods of 20 or 43days after implantation. We conducted clinical assessments and electromyographic examinations, and histological analyses were conducted in rats euthanised 20, 45, and 82days after surgery. ResultsImmunohistochemical studies revealed tissue damage with similar characteristics to those found in the sporadic forms of ALS, such as overexpression of cystatinC, transferrin, and TDP-43 protein in the cytoplasm. The earliest changes observed seemed to play a protective role due to the overexpression of peripherin, AKTpan, AKTphospho, and metallothioneins; this expression had diminished by the time we analysed rats euthanised on day 82, when an increase in apoptosis was observed. The first cellular changes identified were activated microglia followed by astrogliosis and overexpression of GFAP and S100B proteins. ConclusionOur data suggest that ALS could spread through CSF and that intracerebroventricular administration of cytotoxic ALS-CSF provokes changes similar to those found in sporadic forms of the disease.

New ALS-Related Genes Expand the Spectrum Paradigm of Amyotrophic Lateral Sclerosis.

Amyotrophic Lateral Sclerosis (ALS) is characterized by the degeneration of upper and lower motor neurons. Clinical heterogeneity is a well-recognized feature of the disease as age of onset, site of onset and the duration of the disease can vary greatly among patients. A number of genes have been identified and associated to familial and sporadic forms of ALS but the majority of cases remains still unexplained. Recent breakthrough discoveries have demonstrated that clinical manifestations associated with ALS-related genes are not circumscribed to motor neurons involvement. In this view, ALS appears to be linked to different conditions over a continuum or spectrum in which overlapping phenotypes may be identified. In this review, we aim to examine the increasing number of spectra, including ALS/Frontotemporal Dementia and ALS/Myopathies spectra. Considering all these neurodegenerative disorders as different phenotypes of the same spectrum can help to identify common pathological pathways and consequently new therapeutic targets in these incurable diseases.

14. Autoimmune lower motor neurone disorder – Case report

Motor neurone diseases (MND) traditionally include a broad spectrum of neuromuscular disorders. First, we have to mention sporadic forms of ALS (amyotrophic lateral sclerosis) with mixed clinical presentation (syndromes with upper and lower motor neurone signs), then the isolated central type (primary lateral sclerosis, PLS) and at last the isolated peripheral type (primary muscular atrophy, PMA). The existence of familiar hereditary and genetic MND forms is well known, e.g. superoxide dismutase (SOD-1) and dynactin gene mutations are known to cause PMA variants also called LMND (lower motor neurone disease). Selected LMND cases are associated to specific autoantibodies. For example an asymmetric lower motor neurone syndrome with predominant distal involvement is associated to IgM anti-GM1 or to IgM anti-GalNAc-GD1a. Another LMND variant is an asymmetric lower motor neurone syndrome with particular damage of proximal upper extremities muscles (also known as Vulpian–Bernhard syndrome, brachial amyotrophic diplegia or flail arm syndrome) can be associated in 10–20% cases to anti-asialo GM1 autoantibodies. We present a patient’s case report with suspected Vulpian–Bernhard syndrome with bilateral non-symmetric cervico-brachial amyotrophy without sensory impairment. The autoimmune aetiology was clearly proven by clinical responsiveness to immunosuppression/immunomodulation therapy mainly to repetitive intravenous human polyclonal immunoglobulin application (IVIG).

Genetic analysis of amyotrophic lateral sclerosis in the Slovenian population

Amyotrophic lateral sclerosis (ALS) is a complex fatal neurodegenerative disease characterized by progressive degeneration and loss of upper motor neurons in the cerebral cortex and lower motor neurons in brainstem and spinal cord. We established the frequencies of mutations in 4 major ALS-associated genes, SOD1, TARDBP, FUS, and C9ORF72 in a representative cohort of 85 Slovenian patients with sporadic form of ALS. Pathogenic massive hexanucleotide repeat expansion mutation in C9ORF72 was detected in 5.9% of patients and was the most common cause of the disease. In the remaining 3 genes, we identified 4 changes in 3 patients, p.Val14Met in SOD1, silent mutation p.Arg522Arg in FUS, and p.Gly93Cys in SOD1 together with a novel synonymous variant c.990A>G (p.Leu330Leu) in TARDBP gene, respectively. This study represents the first genetic screening of major causative genes for ALS in a cohort of sporadic ALS patients from Slovenia and is according to our knowledge the first such study in Slavic population. Overall, we genetically characterized 8.2% sporadic ALS patients.

Cellular and molecular mechanisms of motor neuron death in amyotrophic lateral sclerosis: a perspective.

Cellular and molecular mechanisms of motor neuron death in amyotrophic lateral sclerosis: a perspective.

ALS-Associated TDP-43 Induces Endoplasmic Reticulum Stress, Which Drives Cytoplasmic TDP-43 Accumulation and Stress Granule Formation

In amyotrophic lateral sclerosis (ALS) and frontotemporal lobar degeneration, TAR DNA binding protein 43 (TDP-43) accumulates in the cytoplasm of affected neurons and glia, where it associates with stress granules (SGs) and forms large inclusions. SGs form in response to cellular stress, including endoplasmic reticulum (ER) stress, which is induced in both familial and sporadic forms of ALS. Here we demonstrate that pharmacological induction of ER stress causes TDP-43 to accumulate in the cytoplasm, where TDP-43 also associates with SGs. Furthermore, treatment with salubrinal, an inhibitor of dephosphorylation of eukaryotic initiation factor 2-α, a key modulator of ER stress, potentiates ER stress-mediated SG formation. Inclusions of C-terminal fragment TDP-43, reminiscent of disease-pathology, form in close association with ER and Golgi compartments, further indicating the involvement of ER dysfunction in TDP-43-associated disease. Consistent with this notion, over-expression of ALS-linked mutant TDP-43, and to a lesser extent wildtype TDP-43, triggers several ER stress pathways in neuroblastoma cells. Similarly, we found an interaction between the ER chaperone protein disulphide isomerase and TDP-43 in transfected cell lysates and in the spinal cords of mutant A315T TDP-43 transgenic mice. This study provides evidence for ER stress as a pathogenic pathway in TDP-43-mediated disease.

Protein Arginine Methyltransferase 1 and 8 Interact with FUS to Modify Its Sub-Cellular Distribution and Toxicity In Vitro and In Vivo

Amyotrophic lateral sclerosis (ALS) is a late onset and progressive motor neuron disease. Mutations in the gene coding for fused in sarcoma/translocated in liposarcoma (FUS) are responsible for some cases of both familial and sporadic forms of ALS. The mechanism through which mutations of FUS result in motor neuron degeneration and loss is not known. FUS belongs to the family of TET proteins, which are regulated at the post-translational level by arginine methylation. Here, we investigated the impact of arginine methylation in the pathogenesis of FUS-related ALS. We found that wild type FUS (FUS-WT) specifically interacts with protein arginine methyltransferases 1 and 8 (PRMT1 and PRMT8) and undergoes asymmetric dimethylation in cultured cells. ALS-causing FUS mutants retained the ability to interact with both PRMT1 and PRMT8 and undergo asymmetric dimethylation similar to FUS-WT. Importantly, PRMT1 and PRMT8 localized to mutant FUS-positive inclusion bodies. Pharmacologic inhibition of PRMT1 and PRMT8 activity reduced both the nuclear and cytoplasmic accumulation of FUS-WT and ALS-associated FUS mutants in motor neuron-derived cells and in cells obtained from an ALS patient carrying the R518G mutation. Genetic ablation of the fly homologue of human PRMT1 (DART1) exacerbated the neurodegeneration induced by overexpression of FUS-WT and R521H FUS mutant in a Drosophila model of FUS-related ALS. These results support a role for arginine methylation in the pathogenesis of FUS-related ALS.

Abundant FUS-immunoreactive pathology in the skin of sporadic amyotrophic lateral sclerosis

The fused in sarcoma (FUS) protein is a 526 amino acid and its expression is ubiquitous. Recently, mutations in a gene coding FUS have been identified in familial amyotrophic lateral sclerosis (ALS). Also, FUS has been found in neuronal cytoplasmic inclusions in sporadic forms of ALS, suggesting that FUS has an important role in the neurodegeneration occurring in sporadic disease. However, there has been no study of FUS in ALS skin. We made a quantitative immunohistochemical study of the expression of FUS in the skin from patients with sporadic ALS and controls. The proportion of FUS-immunoreactive (ir) cells in the epidermis in ALS patients was significantly higher (P < 0.001) than in controls. There was a significant positive relationship (r = 0.78, P < 0.001) between the proportion and duration of illness in ALS patients. The optical density of FUS-ir cells in the epidermis in ALS patients is markedly stronger (P < 0.001) than in controls. There was a significant positive relation (r = 0.49, P < 0.05) between the immunoreactivity and duration of illness in ALS patients. These data suggest that changes of FUS in ALS skin are related to the disease process, and that metabolic alterations of FUS may take place in the skin of patients with ALS.